Re: [gentoo-amd64] Is there any difference with 4 core?

[P.V.Anthony]

Thank you very much for sharing.

P.V.Anthony

On this day, 03-August-2007 1:41 AM,  Steve Herber wrote:
> The point of Unix has always been to manage resources.  In the old days,
> where you only had a single CPU, the kernel had to time share among all
> the different processes.  The ps command shows you all the different
> processes.  Your system will have many processes.
>
> Once you go to a multiple-cpu system you actually get to take advantage
> of the original Unix choice of fork/exec to create new processes.  Each
> process can run on a different cpu core.  Now instead of timesharing a
> single core across every process, you can have 2 or 4 processes running
> on their own core.
>
> In you sample below, I could see apache running on one core, mysql on
> another, postgres on another, while the applications written in perl,
> ruby, and php running on the 4th.  Of course you will really have
> hundreds of processes running at a time so all 4 cores will have to
> timeshare.  As others said, you don't get 100% from each new core.
> There is overhead from the kernel to figure out where to put a process
> for the next slice and there will be more memory contention because you
> have 4 CPU's talking to memory.  A 4 core system will have almost twice
> the cpu power of a 2 core system.  Most of your processes look like they
> will be IO bound but when a CPU bound tasks runs, it will only take over
> one core leaving the other three to handle the IO bound ones.
>
> Your initial issue is cost and rightly so.  A 2 core system is cheaper
> than a 4 core system.  If you build equivalent 2 core and 4 core systems
> then you could test them against you real workload and see if the 2 core
> system is better.  You might discover that you should really have 2 two
> core systems for the load you have and for redundancy.  Or you might
> discover that you really need to address the IO bottleneck and get
> multiple SCSI data paths.  I would buy a 4 core system with lots of
> disks. Then I would run a test to benchmark my system, probably just
> running top to see the 15 minute load average.  Then I would use the cpu
> control software to disable one, two, and then three cores while my
> normal load was running and I would again look at the 15 minute load
> average.  I would expect to see it rise as the number of CPU's was
> reduced.  My next computer would have the number of cores that met the
> sweet spot.
>
> Cheers!
>
> Steve Herber    herber@×××××.com        work: 206-221-7262
> Security Engineer, UW Medicine, IT Services    home: 425-454-2399
>
> On Thu, 2 Aug 2007, P.V.Anthony wrote:
>
>> On this day, 02-August-2007 4:58 PM,  Pascal BERTIN wrote:
>>>  P.V.Anthony a écrit :
>>>
>>>  <snip/>
>>> >  Apps.
>>> >  1. Gentoo linux 64bit
>>> >  2. Apache 2
>>> >  3. MySql
>>> >  4. Postgres
>>> >  5. Qmail
>>> >  6. Pure-ftpd
>>> >  7. Mod_perl
>>> >  8. php
>>> >  9. ruby
>>> >
>>>  <snip/>
>>>
>>>  aren't you forgetting the app that you will run the most :
>>>  emerge.
>>>
>>>  This one will really benefit from quad core, and during time where you
>>>  will work on the server.
>>>  So, facing such a choice, I would also consider my comfort/time, and
>>>  give quad core a +1.
>>>
>>>  Pascal
>>
>> What I am really interested is, how the server will perform most of
>> the time. Will the instance of the apps go to each core in a balanced
>> way?
>>
>> From the previous posts, I gather that the amd chip is really good.
>>
>> I must say that I love the intel drivers for the network and sata. If
>> only amd has some chip sets for their own cpus and good open source
>> drivers for their chip sets. Intel has that covered and I think the
>> intel drivers are open source.
>>
>> Please correct me if I am wrong.
>>
>> P.V.Anthony
>>
>> --
>> gentoo-amd64@g.o mailing list
>>
>
> !DSPAM:6,46b21781197995167217508!

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